Effects of exogenous γ-aminobutyric acid on the growth and cadmium content of lettuce under cadmium-stress conditions

γ-Aminobutyric acid (GABA) plays an important role in plant resistance to abiotic stress, but the mechanisms underlying GABA-mediated alleviation of Cd stress in leafy vegetables have not yet been elucidated. Therefore, this study aims to investigate the effects of different GABA concentrations on the growth and Cd content of lettuce (Lactuca sativa L.) under Cd stress conditions. The results indicate that Cd stress (50 μ mol/L) significantly inhibited lettuce growth, decreased chlorophyll content, and increased osmoregulatory compound content. Under Cd stress conditions, the exogenous application of 1 and 2 g/L GABA significantly increasing lettuce's plant height and biomass. At the same time, application of 1 and 2 g/L GABA reduced the Cd content in the shoots and roots of lettuce, by 4.92%–12.16% compared to Cd treatment alone. In addition, GABA treatment of 1 and 2 g/L also alleviated the decrease in the antioxidant enzyme activities and reduced the osmoregulatory compound content increase caused by Cd stress, thereby alleviating Cd-induced oxidative damage. The results of the PCA and correlation analysis indicate that the effects of GABA can be explained by changes in cadmium content, photosynthetic pigment levels, and antioxidant enzyme activities. Overall, these results provide a reference for the mechanisms underlying the GABA-mediated reduction in Cd content in lettuce.